Control handle for a contact force ablation catheter

ABSTRACT

A control handle for a steerable catheter body for navigation of the catheter body through a biological lumen and manipulation at a treatment site. The control handle includes a housing assembly that houses a piston assembly and a resistance adjusting assembly. The resistance adjusting assembly can be adjusted to provide the desired frictional characteristics of the user for control of the resistance between the piston assembly and the housing assembly. In one embodiment, the piston assembly is configured to provide a frictional resistance that varies dynamically to substantially match the restorative force across the range of catheter tip deflection. Other embodiments include a vibrating member that provides tactile feedback to the operator to indicate conditions at the distal end of the catheter, such as contact force.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 14/562,370, filed 5 Dec. 2014, now U.S. Pat. No.10,034,706, issued 31 Jul. 2018 (the '370 application); which is acontinuation application of U.S. patent application Ser. No. 13/084,214,filed 11 Apr. 2011, now U.S. Pat. No. 8,906,013, issued 9 Dec. 2014 (the'214 application). This application claims the benefit of U.S.Provisional Patent Application No. 61/322,670 (the '670 application),filed 9 Apr. 2010; U.S. Provisional Patent Application No. 61/381,643,filed 10 Sep. 2010 (the '643 application); and U.S. Provisional PatentApplication No. 61/409,379, filed 2 Nov. 2010 (the '379 application).The '370 application; the '214 application; the '670 application; the'643 application; and the '379 application are hereby incorporated byreference as though fully set forth herein.

FIELD OF THE DISCLOSURE

The invention is generally directed to a steerable ablation cathetersystem with a deflectable tip. More specifically, the invention isdirected to a control handle adapted to control the deflection of asteering spine within a patient's body.

BACKGROUND OF THE DISCLOSURE

Catheter ablation is a surgical procedure in which a catheter having anablation tip is fed through various biological lumens to reach targetedtissue within the body. Radiofrequency current (“RF current”) istransmitted through electrodes disposed within the biological lumen andemitted from the ablation tip into the targeted tissue. The ablation tipis placed in close proximity to or in contact with the targeted tissueto maximize the amount of RF current supplied directly to the targetedtissue and limit the amount of untargeted tissue exposed to the RFcurrent. Because the ablation catheter is navigated through existingbiological lumen to reach the targeted tissue, catheter ablation surgeryis less invasive than other available surgical techniques for reachingthe targeted tissue, such as open heart surgery.

However, biological lumens and particularly blood vessels are oftencircuitous in nature and typically intersect many other biologicallumens, presenting challenges with respect to catheter navigationtherethrough. In order to reach the targeted tissue, the ablation tipmust be threaded through the bends in the biological lumen and throughthe various intersections to reach the targeted tissue. Once near thetarget tissue, the operator must be able to accurately position the tipof the catheter for adequate delivery of the ablation energy. Thedifficult navigation process required can extend the surgical timeconsiderably and can result in injury to the patient.

Catheter bodies often comprise an internal pull wire for deflecting thetip of the catheter body to more easily navigate the various turns andbends of the biological lumen. The pull wire is typically affixedproximate the tip of the catheter body and extends through the catheterbody exiting the end of the catheter body that remains outside thepatient's body. An operator can apply a pulling force to the pull wireto cause the tip of the catheter to deflect. Handles are often affixedto the proximal end of the catheter body to manipulate the pull wire forcontrol of the defection of the catheter. However, different operatorsoften have different tactile preferences as to the amount of forcerequired to deflect the tip of the catheter a given amount. Astandardized or factory set force-to-deflection relationship may causesome operators to over-deflect the catheter tip (thus denying theoperator resolution in deflecting the tip), while causing othersdiscomfort because the force requirement for a given tip deflection isuncomfortably high.

One steering mechanism used for deflection of a catheter tip is theso-called “steering spine.” Steering spines are characterized by acontinuous portion (i.e. the “spine”) that extends from the proximal tothe distal end of the steering mechanism. An advantage of the steeringspine is that the resilience or elasticity of the continuous spineportion generates its own restorative force when the spine is deflectedfrom its at-rest position, thus negating the need for a second pull wireto restore the tip to a straightened geometry.

The restorative force exerted on the pull wire by a steering spinetypically depends on the nominal deflective position of the steeringspine. That is, the restorative force exerted by the steering spine canbe substantially less when the steering spine is near a slack or neutral(un-deflected) orientation than when the steering spine is nearly fullydeflected. For the frictional force to counter the restorative forceacross the range of tip deflection, the frictional force needs to be sethigh enough to counter the steering spine at the maximum restorativeforce (i.e. at the maximum tip deflection). Meanwhile, the operatortypically spends most of the time with the tip at or near the neutralorientation. Thus, the operator has to overcome a high frictional forcewhen the tip is proximate the neutral orientation, which can lead tooperator fatigue and poor positional resolution.

Operating rooms can be the host to a plethora of sounds. At any giventime during a surgical procedure, several instruments can be emittingaudio sounds in vying for the attention of attending personnel. Cathetersystems that utilize sound to alert an operator can, in some instances,lose effectiveness as being yet another sound among the cacophony.

A device that can accommodate the tactile preferences of an individualoperator in the control of catheter tip deflection would be welcome. Africtional device that can substantially match the varying restorativeforce of the steering spine across the range of tip deflection whilereducing the force requirements at low tip deflections would also bewelcome. A catheter system that implements non-auditory sensoryperceptions would also find utility in the modern operating room.

SUMMARY OF THE DISCLOSURE

Various embodiments of the invention are directed to better control oftip deflection for catheters that utilize a steering spine for controlof tip deflection. Typically, the restorative force of a steering spineis opposed at least in part by components that generate a frictionalforce within the steering handle. Certain embodiments of the inventionprovide an adjustable friction mechanism within the handle allowing anoperator to adjust and attain a balance between the restorative andfrictional forces suitable to the individual operator to provide adesired actuation force magnitude to overcome this balance.

Other embodiments provide a frictional force that varies dynamicallywith the restorative force of the steering spine across the range of tipdeflection. Certain embodiments of the invention provide for variablefriction across the range of deflection of the steering spine withoutneed for manually adjusting the friction at each nominal deflectionposition. The variable friction enables the counterbalancing frictionalforce to change with and substantially match the restorative forceacross the deflection range of the steering spine.

The control handle according to an embodiment of the invention isadapted to apply an adjustable frictional force as a counterbalance tothe restorative force. The applied frictional force (and subsequentsteady state force) can be adjusted manually by an operator according tothe operator's tactile preference. The frictional force can be adjustedso that the balance requires an operator to apply a pull force toincrease the deflection of the steerable tip and a pushing force todecrease the deflection of the steerable tip. Also, in one embodiment,the frictional force mechanism can be configured so that the frictionalforce substantially equals the restorative force across the deflectiverange of the steerable tip.

Structurally, the control handle can comprise a housing assembly and apiston assembly. The housing assembly includes a guide for centering thepiston assembly. The piston assembly further comprises a central slideradapted to slide axially relative to the guide. The guide is adapted toreceive the proximal extremity of the pull wire such that sliding thehousing assembly relative to the central slider applies a pull force tothe pull wire to defect the steerable tip. The central slider canfurther comprise a steering knob adapted to allow an operator to holdthe central slider in place while sliding the housing assembly to applya pull force to the pull wire.

The control handle can further comprise a resistance adjusting assemblyadapted to apply a frictional force that resists the piston assembly. Inone embodiment, the resistance adjusting assembly comprises a knob and adeformable o-ring or gasket. The piston assembly further comprises anexterior glide surface operatively coupled with the central slider thatslidably engages the deformable gasket. Tightening the knob applies adeforming force to the deformable gasket causing the gasket to constrictinward against the glide surface of the piston assembly thereby manuallyincreasing the friction between the piston assembly and the housingassembly to dampen the movement of the central slider and provide acounteracting frictional force to the restorative force.

According to an embodiment of the invention, the glide surface can beangled or tapered relative to the central axis of the slider such thatthe clearance between the housing assembly and the glide surface changesat the point or line of contact between the deformable gasket and theglide surface as the piston assembly is translated in an axialdirection. The changing clearance in turn alters the compression of theo-ring or gasket, thereby changing the friction between the centralslider and the housing assembly. The dynamically changing frictionalforce that varies with the position of the central slider allows thecontrol handle to maintain the deflection of the steerable tip at anydeflection while closely matching the restorative force of the steeringspine, thus requiring less frictional force that needs to be overcomewhen operating near the neutral orientation.

According to an embodiment of the invention, the handle can furthercomprise a tactile feedback device for providing a physical sensation tothe user corresponding to the force applied to the tip of the cathetersystem. The tactile feedback device can provide a tactile stimulus, suchas a vibration, that varies in a characteristic (e.g., intensity,amplitude or frequency) and in relation to an operating conditionexperienced at the end effector of the catheter (e.g., contact force,ablation intensity or duration, force-time integration). Thecharacteristic of the tactile stimulus can range from a low orintermittent characteristic when the operating condition initiallycrosses some threshold to an increasingly pronounced characteristic asthe operating condition reaches or exceeds a desired state or enters anexcessive state. According to an embodiment of the invention, thetactile feedback device can comprise a vibrating motor to provide atactile vibrating sensation. The feedback device can additionallycomprise an auditory device providing an audible physical sensation.

The above summary of the various representative embodiments of theinvention is not intended to describe each illustrated embodiment orevery implementation of the invention. Rather, the embodiments arechosen and described so that others skilled in the art can appreciateand understand the principles and practices of the invention. Thefigures in the detailed description that follow more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic of the components of a catheter system accordingto an embodiment of the invention;

FIG. 2 is a plan view of a control handle according to an embodiment ofthe invention;

FIG. 3 is a sectional side view of the control handle of FIG. 2 ;

FIG. 4 is an exploded perspective view of a control handle of FIG. 2 ;

FIG. 5 is an enlarged partial sectional side view a control handlehaving an angled glide surface according to an embodiment of theinvention;

FIG. 6 is a representative view of a catheter at or near a neutralorientation of a steerable tip according to an embodiment of theinvention;

FIG. 6A is an enlarged partial sectional side view of the control handlein the orientation of FIG. 6 ;

FIG. 7 is a representative view of a catheter in an intermediate flexedorientation of a steerable tip according to an embodiment of theinvention;

FIG. 7A is an enlarged partial sectional side view of the control handlein the orientation of FIG. 7 ;

FIG. 8 is a representative view of a catheter in a fully flexedorientation of a steerable tip according to an embodiment of theinvention;

FIG. 8A is an enlarged partial sectional side view of the control handlein the orientation of FIG. 8 ;

FIG. 9 is a graph of the forces of operation of various embodiments ofthe invention; and

FIG. 10 is a sectional side view of a control handle with a vibratingmotor.

FIGS. 11A and 11B are sectional views of resistance adjusting assembliesin embodiments of the invention.

DETAILED DESCRIPTION OF THE FIGURES

Referring to FIG. 1 , a catheter system 20 is depicted in an embodimentof the invention. The catheter system 20 comprises an elongated catheterassembly 22 having a proximal portion 24, a middle portion 26 and adistal portion 28. A catheter shaft 30 defines the outer radial surfaceof catheter assembly 22. The distal portion of catheter assembly 22includes a steering section 32 and an end effector 34. Catheter system20 can be equipped with instrumentation for determination of at leastone operating condition of catheter assembly 22 (e.g., temperature,contact force, contact impedance, irrigation flow). In some embodiments,the instrumentation is disposed in end effector 34. Steering section 32further comprises a pull wire 35 (depicted in FIG. 3 ) disposed withinelongated catheter assembly 22 and affixed to the distal end of steeringsection 32, wherein apply a pulling force to the pull wire causessteering section 32 to deflect. In one embodiment, the steering section32 comprises a steering spine (not depicted). In one embodiment,proximal portion 24 is operatively coupled with a control handle 36.

Control handle 36 may be operatively coupled with a controller 38containing various appurtenances that augment the operation of thecatheter system 20. Non-limiting examples of the appurtenances ofcontroller 38 include power sources and/or irrigation systems forsourcing the end effector 34, optical sources for sourcing fiber opticsystems within the catheter system 20, data acquisition devices formonitoring instrumentation of the catheter system 20, and/or controlsystems for controlling the sourcing of the end effector 34. Controller38 can be configured to receive an input signal or signals 42 fromcatheter assembly 22 and to produce an output signal or signals 44 tocatheter assembly 22. Controller 38 can be coupled to control handle 36and catheter assembly 22 via a cable 46. Cable 46 can containinstrumentation leads, power source leads, irrigation lines and/or fiberoptics. In some instances, certain input signal(s) 42 and outputsignal(s) 44 are transmitted wirelessly (i.e. without being routedthrough cable 46), such as by radio transmitter and receiver.

In certain embodiments, a tactile feedback device 50 is operativelycoupled to control handle 36. Tactile feedback device 50 can be any of avariety of devices that produce tactile stimulus, such as vibration,electrical impulses or temperature change. According to an embodiment ofthe invention, an auditory speaker (not depicted) for providing anaudible sound can also be provided.

In operation, the instrumentation of catheter assembly 22 detects atleast one operating condition of catheter assembly 22, and sends inputsignal 42 to controller 38. Examples of operating parameters upon whichthe operating condition can be predicated includes a force, atemperature, a timer that provides a duration or delay, and/or anirrigation flow. Some of these parameters can be sensed by input signal42 to controller 38; others can be commensurate with the operation of acomponent within controller 38, thus requiring no input signal per se.

In some embodiments, controller 38 receives input signal 42 and isconfigured to send output signal 44 to tactile feedback device 50 ifinput signal 42 corresponds to a known or predetermined conditionregarding the operation of catheter assembly 22. Output signal 44, whenpresent, causes tactile feedback device 50 to generate a tactilestimulus in or on control handle 36 that is sensed by the operator.

For example, in some embodiments, the instrumentation can include aforce sensing assembly contained within or operatively coupled with endeffector 34 for detection of contact force between an organ or vesseland end effector 34. Non-limiting examples of force sensing assembliesare disclosed at U.S. Patent Application Publication Nos. 2006/200049,2007/060847, 2008/0294144, 2009/287092, 2009/177095 to Leo et al. andU.S. Patent Application Publication No. 2008/009750 to Aeby et al., allof which are assigned to assignee of this application, and thedisclosures of which are hereby incorporated by reference in theirentirety herein except for express definitions contained therein. Forsuch an embodiment, controller 38 can be configured to accept inputsignal or signals 42 from the force sensor, and to produce output signal44 to tactile feedback device 50 if input signal(s) 42 from the forcesensor correspond to a contact force that exceeds a certain magnitude orfalls within a certain range of magnitudes. Tactile feedback device 50will then produce a tactile stimulus (e.g., a vibration), telling theoperator that the contact force is over a certain threshold or within acertain range.

In another example, end effector 34 can be fitted with an ablation headand controller 38 equipped with an energy source. In this embodiment,controller 38 could be configured to send output signal 44 to tactilefeedback device 50 only when the ablation head is energized. It is notedthat controller 38 can be configured generate output signal 44concurrently with energization of the ablation head, and as such doesnot receive an input signal.

In addition, controller 38 can be configured to produce output signal 44and subsequent tactile stimulus to have certain characteristics thatdepend on the relative state or magnitude of the operating condition.Returning to the example of contact force, and by way of furtherexample, controller 38 can be configured to output a steady outputsignal 44 when input signal(s) 42 correspond to a contact force that iswithin a desired range of operation, and to output an intermittentoutput signal 44 when input signal(s) 42 correspond to a contact forcethat exceeds the desired range of operation. For a configuration whereintactile feedback device 50 is a vibrating motor, the operator would knowthat a steady vibration is an indication that the contact force is atthe desired level, and that an intermittent vibration is an indicationthat the contact force is too great. Other characteristics can also beimplemented by proper manipulation of output signal 44, such as steadybut increasing vibration as the contact force is increased throughdesired range, changing to a pulsed vibration when exceeding the desiredforce range.

Another characteristic of tactile stimulus is vibration frequency.Tactile feedback device 50 could be configured to output a varyingvibration frequency that varies with, for example, a voltage level ofoutput signal 44 from controller 38. Or tactile feedback device 50 couldcomprise two vibrating motors, each producing a different vibrationfrequency. With these arrangements, controller 38 and tactile feedbackdevice 50 could be configured to produce vibration frequencies thatindicate the various magnitudes of the contact force. The changingfrequencies of vibration can also produce an auditory stimulus,providing the operator with further sensory capability.

In some embodiments, controller 38 can include analog electroniccomponents to execute the control logic required to monitor inputsignal(s) 42 and produce output signal 44 when certain predeterminedconditions of operation are met. In other embodiments, controller 38comprises digital components such as a microprocessor that accessesprogrammed instructions from a digital memory device, wherein theinstructions can comprise the steps of receiving input signal(s) 42,determining whether catheter assembly 22 is in a predetermined conditionof operation, and sending output signal 44 to tactile feedback device50. In still other embodiments, controller 38 is includes both analogand digital components. Controller 38 can comprise a general purposecomputer, or a specialized console configured for operation only withcatheter system 20.

Referring to FIGS. 2 through 4 , a control handle 150 is depicted in anembodiment of the invention. Control handle 150 comprises a housingassembly 152, a steering or piston assembly 154 and a resistanceadjusting assembly 156, all concentric about a central axis 157. Pistonassembly 154 can comprise a steering knob 174, a central slider 176 anda glide assembly 181. In various embodiments, piston assembly 154includes at least one notch or slot 186 that extends axially along aportion of central slider 176. Piston assembly 154 also includes a lockor transition piece 182 defining a seat lumen or cavity 184. In oneembodiment, transition piece is disposed in the proximal end of steeringknob 174 and glued into place. Piston assembly 154 also includes a glidesurface 187 defined by the exterior of the glide assembly 181. Steeringknob 174 is affixed to or is integral with central slider 176 andadapted to allow a user to hold or change the position of central slider176 within housing assembly 152.

Housing assembly 152 includes a proximal portion 160 having a proximalend 161 and a distal portion 162 having a distal end 163. Housingassembly 152 also defines a housing lumen or central bore 158 concentricabout central axis 157. Central bore 158 can further comprise a threadedportion 170 adapted to adjustably engage a slider housing or pistonguide 178 adapted to receive a portion of piston assembly 154. Pistonguide 178 includes a smooth bore 188 adapted to slidably receive centralslider 176 and can further include a threaded exterior 192 foradjustable engagement with threaded portion 170 of central bore 158.Piston guide 178 can be coupled with a split pin 180 that extends intoor across the piston guide 178 and into or through the slot 186 of thecentral slider 176. Split pin 180, when implemented, can furthercomprise a pull wire notch 212 and a pull wire crimp 214 for capturingthe proximal end of pull wire 35. In one embodiment, piston guide 178includes access holes 215 for mounting split pin 180. Proximal portion160 can further comprise a port 164 having a threaded portion 166adapted to operably engage resistance adjusting assembly 156 and alsocan comprise a radial step 167 that defines a shoulder 168 at the baseof port 164. In one embodiment, shoulder 168 cooperates with a bearingface 198 of resistance adjusting assembly 156 to define a gland 169. Inone embodiment, a deformable gasket 196, such as an o-ring, is disposedin gland 169. The gland 169 can be continuous.

In some embodiments, resistance adjusting assembly 156 comprises athreaded member 194 and a bushing 199. Threaded member 194 is adapted toadjustably engage threaded portion 166 of port 164. Gland 169 defines avolume that can be varied with the position of bushing 199 and/orthreaded member 194. In some embodiments, bushing 199 is a washer, asdepicted in FIG. 4 .

Threaded member 194 can further comprise a grip 195 adapted to assistusers in rotating threaded member 194. Bushing 199, when implemented, isdisposed between threaded member 194 and deformable gasket 196 to definebearing surface 198.

Functionally, threaded member 194 applies a compressive force againstdeformable gasket 196 causing deformable gasket 196 to deform radiallyagainst glide surface 187 of glide assembly 181, thereby providingfriction between glide assembly 181 and deformable gasket 196. Thefriction creates resistance between the piston assembly 154 and housingassembly 152, and can provide better control in manipulation of pistonguide 178 and in the amount of tension force on the pull wire. Bushing199 prevents rotational forces caused by the tightening of threadedmember 194 from twisting or damaging deformable gasket 196.

In some embodiments, elongated catheter assembly 22 extends throughsteering knob 174, with catheter shaft 30 terminating within transitionpiece 182. Pull wire 35 can extend proximally through transition piece182 and is coupled to split pin 180. Transition piece 182 can include aslot that extends along one side and enables instrumentation leads thatextend from catheter assembly 22 to be routed laterally away fromcentral axis 157. By this arrangement, all of the components of catheterassembly 22 ride along with piston assembly 154, except for pull wire 35which rides along with housing assembly 152, so that relative movementbetween piston assembly 154 and housing assembly 152 causes pull wire 35to be longitudinally displaced relative catheter assembly 22.

Piston assembly 154 can further comprise a chuck 200 affixed to centralslider 176 and adapted to receive cable 46 from controller 38. Chuck 200includes a plurality of locking arms 202 and a compression fitting 204.Once cable 46 is in place within locking arms 202, compressing fitting204 is slid over plurality of locking arms 202 closing locking arms 202over a portion of cable 46 to lock in place. In one embodiment of theinvention, deformable gasket 196 of resistance adjusting assembly 156 isdeformed against chuck 200 to create friction between central slider 176and housing assembly 152.

In operation, an operator pushes or pulls the piston assembly 154 sothat it translates axially relative to the housing assembly 152 betweena first position and a second position. This motion also causes glideassembly 181 to translate relative to housing assembly 152 and to causesplit pin 180 to slide relative to slot 186 of central slider 176.Translation of split pin 180 also translates pull wire 35 withincatheter assembly 22. Pull wire 35 is maintained in a tension state overat least part of the range of motion of split pin 180 with slot 186, thetension being caused by the position of split pin 180 within slot 186and the restorative force of steering section 32. Translation of pistonassembly 154 in the distal direction relative to housing assembly 152acts to increase the deflection of steering section 32 and increase thetension force on pull wire 35. In contrast, translation of pistonassembly 154 in the proximal direction relative to housing assembly 152acts to reduce the deflection of steering section 32 and decrease thetension of pull wire 35. The catheter system 20 is generally configuredso that at some point, the position of the piston assembly 154 relativeto the housing assembly 152 causes steering section 32 to return to arelaxed position, depending on the resilience of steering section 32.

Referring specifically to FIG. 3 , housing assembly 152 can furthercomprise a first shoulder 206 adapted to stop glide assembly 181. Firstshoulder 206 limits the distance piston assembly 154 can travel in adistal direction relative to housing assembly 152. Housing assembly 152can also comprise a second shoulder 224 opposite first shoulder 206 forengaging an opposing shoulder 226 formed on central slider 176. Secondshoulder 224 engages opposing shoulder 226 to limit the distance pistonassembly 154 can travel in a proximal direction relative to housingassembly 152. In one embodiment of the invention, housing assembly 152further comprises at least one cushioning or spacer gasket 208 (twodepicted in FIG. 3 ) disposed between glide assembly 181 and shoulder206. Spacer gasket(s) 208 can comprise a rubber or synthetic rubbero-ring. Central slider 176 and/or glide assembly 181 can be adapted tomaintain the position of spacer gasket(s) 208 along central slider 176between glide assembly 181 and housing assembly 152.

Functionally, limiting the travel distance of piston assembly 154 withinhousing assembly 152 can prevent overextension of pull wire 35, as wellas excessive slack in pull wire 35. Spacer gasket(s) 208 can furtherlimit the travel distance of piston assembly 154 within housing assembly152, as well as preventing damage to housing assembly 152 or pistonassembly 154.

In some embodiments, proximal portion 24 of elongated catheter assembly22 passes through a flexible stress reliever 216 attached to the distalend of distal portion 162 to prevent excessive bending at the junctionbetween handle 150 and elongated catheter assembly 22. Optionally,stress reliever 216 can be integral with proximal portion 24.

Transition piece 182 can further comprise a notch 218 through theexterior of transition piece 182 into cavity 184. Notch 218 enableselectrodes disposed within elongated catheter assembly 22 to passthrough transition piece 182 and to controller 38 powering theelectrodes. Transition piece 182 can also further comprise a safetylumen 210 adapted to receive a thread (Kevlar; not depicted) disposedwithin elongated catheter assembly 22. Safety lumen 210 allows users toretrieve a broken or severed elongated catheter assembly from the bodyof a patient by pulling on the safety thread.

Referring to FIGS. 5-8 , a tapered glide assembly 181 a is depictedaccording to an embodiment of the invention. Tapered glide assembly 181a comprises frustum an angled glide surface 218 having a proximal edge220 and a distal edge 222. Angled glide surface 218 is tapered radiallyinward from proximal edge 220 to distal edge 222 such that the outerdiameter of tapered glide assembly 181 a is narrower at distal edge 222than proximal edge 220.

In operation, as depicted in FIGS. 6-8 and 6A-8A, angled glide surface218 varies the radial distance between tapered glide assembly 181 a andgland 169 at the location of deformable gasket 196 as central slider 176is axially translated. Translation of piston assembly 154 in a distaldirection (i.e. forward) relative to housing assembly 152 increases thedeflection of steering section 32, which increases the restorative forceexerted on pull wire 35. Correspondingly, forward translation of pistonassembly 154 also decreases the radial distance between tapered guideassembly 181 a and gland 169. When deformable gasket 169 is in contactwith tapered guide assembly 181 a, the reduction in radial distanceincreases the compression of deformable gasket 196, thereby increasingthe friction between piston assembly 154 and housing assembly 152. Theincreased friction caused by sliding piston assembly 154 forwardrelative to housing assembly 152 can be tailored to correspond generallywith the increased restoring force caused by the increased deflection ofsteering section 32.

In similar fashion, translation of piston assembly 154 in a proximaldirection (i.e. backward) relative to housing assembly 152 reduces thedeflection steerable section 32 and the attendant restorative forceexerted on pull wire 35. The frictional force generated by deformablegasket 196 is decreased by virtue of an increase in the radial distancebetween glide assembly 181 and piston guide 178 at deformable gasket196. As such, translating piston assembly 154 to increase deflection ofsteering section 32 increases both the restorative force exerted bysteering section 32 and the counteracting frictional force that countersthe restorative force, while translating piston assembly 154 to reducedeflection of steering section 32 decreases both the restorative forceand the counteracting frictional force.

According to an embodiment of the invention, central slider 176 andglide assemblies 181, 181 a can each comprise interlocking threads suchthat central slider 176 and glide assemblies 181, 181 a can be easilyscrewed together and separated. As such, either glide assembly 181 or181 a can separated from piston assembly 154 and replaced with analternatively configured glide assembly 181 having a linear glidesurface such as the parallel glide surface 187 and an angled glidesurface 218 or a non linear glide surface. The modularity of glideassembly 181, 181 a enables users to easily interchange glide assemblies181 having different glide surfaces 218 to suit the user's preferencesor the requirements of the particular medical procedure to be performed.Furthermore, glide assemblies 181, 181 a can be manufactured by amachined process that produces glide assemblies 181, 181 ainexpensively. Similarly, glide assembly 181 or 181 a can be easilyremoved from central slider 176 to change the number of spacer gaskets208, further increasing the modularity and customizability of controlhandle 150.

In assembly, central slider 176 is inserted into piston guide 178, andsplit pin 180 is fed through both access holes 215 of piston guide 178and slot 186 of central slider 176. Catheter assembly 22, with pull wire35 extending from proximal portion 24, is laid out with disassembledcomponents including steering knob 174, distal portion 162, cavity 184and the central slider 176/piston guide 178 combination. The proximalend of pull wire 35 is then threaded through these components and fedthrough pull wire notch 212 of split pin 180. Steering knob 174 is thenfed through distal portion 162 and attached to central slider 176.Distal portion 162 of housing assembly 152 is threaded over the threadedexterior 192 of piston guide 178. Distal portion 162, now attached topiston guide 178, is axially positioned so that split pin 180 is at adesired position within slot 186 for the neutral position of steeringsection 32. Pull wire 35 is secured to split pin 180 by setting crimp214 into split pin 180, which crimps pull wire 35 within split pin 180.Proximal portion 160 of housing assembly 152 can then be threaded overpiston guide 178 and brought into contact with distal portion 162. Thecontact between proximal and distal portions 160 and 162 locks thehousing assembly 152 in place.

In one embodiment, the clearance between access holes 215 and split pin180 can affect a press fit on the unsplit end of split pin 180.Alternatively, split pin 180 can affect a looser, sliding fit initially,with the action of setting crimp 214 causing split pin 180 to be setwithin access holes 215.

Pull wire 35 may subsequently creep after being under tension for sometime, creating slack or a dead band in the operation of the handle 150.Adjustment to eliminate the slack can be accomplished by breakingcontact between proximal and distal portions 160 and 162 of housingassembly 152 (e.g., by turning back the proximal portion 160) androtating distal portion 162 about piston guide 178 to adjust theposition of the distal portion 162 relative to piston guide 178 andeliminate the slack. Proximal portion 160 is then brought back intocontact with distal portion 162 to again lock the proximal and distalportions 160 and 162 together. Alternatively, the same procedure can befollowed to relieve excessive tension in pull wire 35 when the catheterassembly 22 is in the neutral orientation.

Referring to FIG. 9 , a force vs. handle displacement graph 240 of theforces of operation of various embodiments of the invention arepresented. The abscissa of graph 240 presents the “handle displacement”242, that is, the linear displacement of central slider 176 withinhousing assembly 152. The minimum of handle displacement 242 (FIGS. 6and 6A) corresponds to substantially no tip deflection (origin of graph240) and the maximum of handle displacement 242 corresponds to a maximumtip deflection (FIGS. 8 and 8A) at the maximum of the abscissa. Theordinate of graph 240 represents the force 244 exerted on the pull wire.

A restorative force curve 248 represents the actuation force exerted onthe pull wire to further increase the displacement of central slider176. A constant frictional force curve 250 represents the actuationforce exerted on the pull wire to further increase the displacement ofcentral slider 176 in the presence of a substantially constantfrictional force exerted on central slider 176 by deformable gasket 196.A variable frictional force curve 252 represents the actuation forceexerted on the pull wire to further increase the displacement of centralslider 176 in the presence of a variable frictional force exerted oncentral slicer 176 by deformable gasket 196.

To hold steering section 32 at any given deflection, the frictionalforce must exceed the restorative force curve 248 at any given point onthe abscissa of graph 240. Because a constant frictional force deviceexerts a fixed frictional force regardless of handle displacement 242, aconstant frictional force 256 must exceed a maximum force 258 of therestorative force curve 248.

However, with a variable frictional force device, such as depicted atFIG. 5 , variable frictional force curve 252 can be tailored to exceedthe restorative force locally along the abscissa of graph 240. Thisenables a variable frictional device to operate at lower actuationforces at lower handle displacement 242 (i.e. at lower tip deflections).The result is that driving the tip from no deflection to maximumdeflection requires substantially less energy with the variablefrictional device. An energy savings 260 that results is depicted by thecross-hatched area on the graph 240. The significance of reduced energyis lower operator fatigue over the course of a surgical procedure.

Referring to FIG. 10 , a vibrating motor 262 for inducing a vibrationthat can be sensed on housing assembly 152 is depicted in assembly withhandle 150 according to an embodiment of the invention. Vibrating motor262 can comprise a conventionally shaped vibrating motor such as themini vibrating motor (DCM-382) or pancake shaped vibrating motor(DCM-373) available from All Electronics Corp. of Van Nuys, Calif.,U.S.A. Vibrating motor 262 can be implemented as tactile feedback device50 of FIG. 1 to provide a physical sensation with increasing amplitudeand/or intensity to the user as the force applied to the catheter tipexceeds a predetermined “safe” threshold and increases above thethreshold.

Referring to FIGS. 11A and 11B, alternative resistance varyingassemblies 156 a and 156 b are presented in embodiments of theinvention. In these configurations, threaded members 194 a and 194 b,respectively, can comprise set screws. For resistance varying assembly156 a, threaded member 194 a is oriented to engage bushing 199 in aradial direction. To adjust the resistance of the control handle 150,bushing 199 is exerted against deformable gasket 196 to provide thedesired resistance, then set in place using threaded member 194 a. Forresistance varying assembly 156 b, threaded member 194 b is oriented toengage bushing 199 in a canted direction (i.e. between a purely axialand a purely radial orientation).

To adjust the resistance of the control handle 150, threaded member 194b is adjusted to motivate bushing 199 to exert against deformable gasket196 and provide the desired resistance. Threaded member 194 b registersinside a notch or groove 250 to exert a force having an axial componenton bushing 199. Threaded member 194 b can be held in position usingthread locking paste or by other ways known in the art.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example only. It isunderstood that the intention of the foregoing descriptions anddepictions are not to limit the invention to the particular embodimentsdescribed. To the contrary, the intention is to cover all modifications,equivalents, and alternatives falling within the spirit and scope of theinvention as defined by the appended claims.

For purposes of interpreting the claims for the invention, it isexpressly intended that the provisions of Section 112, sixth paragraphof 35 U.S.C. are not to be invoked unless the specific terms “means for”or “step for” are recited in the subject claim.

The invention claimed is:
 1. A steerable catheter, comprising: acatheter shaft; a control handle coupled to the catheter shaft, thecontrol handle comprising: a housing assembly having a proximal portionand a distal portion and defining a central axis, wherein the proximalportion defines a central bore concentric with the central axis, thecentral bore including a radial step that defines a shoulder concentricabout the central axis; a deformable gasket disposed adjacent to theradial step; and a tapered glide assembly disposed within the centralbore of the housing assembly, the tapered glide assembly comprising afrustum which extends into and beyond the central bore of the housingassembly, the frustum defined by an angled glide surface extending alongthe entire longitudinal length of the frustum, wherein the angled glidesurface is tapered radially inward from a proximal edge to a distal edgeof the angled glide surface, and wherein the angled glide surface is incontact with the deformable gasket in the central bore of the housingassembly, wherein translation of the tapered glide assembly in thedistal direction causes a distal end of the catheter to deflect.
 2. Thesteerable catheter of claim 1, wherein the angled glide surface istapered radially inward from the proximal edge of the angled glidesurface to the distal edge of the angled glide surface, such that anouter diameter of the tapered glide assembly is narrower at the distaledge than the proximal edge.
 3. The steerable catheter of claim 2,wherein the translation of the tapered glide assembly in the distaldirection further generates an increased frictional force between thedeformable gasket and the angled glide surface.
 4. The steerablecatheter of claim 3, wherein the increased frictional force counteractsa restorative force of the catheter shaft, the restorative force beinggenerated in response to the deflection of the catheter shaft.
 5. Thesteerable catheter of claim 2, wherein the translation of the taperedglide assembly in a proximal direction generates a decreased frictionalforce between the deformable gasket and the angled glide surface.
 6. Thesteerable catheter of claim 1, wherein the angled glide surfacecomprises a non-linear glide surface.
 7. The steerable catheter of claim1, further comprising a resistance adjusting assembly coupled to adistal end of the housing assembly, wherein the resistance adjustingassembly defines a bearing surface disposed at a distal end of theresistance adjusting assembly.
 8. The steerable catheter of claim 7,wherein the bearing surface and the radial step define a gland in whichthe deformable gasket is disposed.
 9. The steerable catheter of claim 8,wherein the resistance adjusting assembly is configured to moveproximally and distally to adjust a size of the gland.
 10. The steerablecatheter of claim 9, wherein a friction between the deformable gasketand the angled glide surface is adjusted in response to the adjustmentin the size of the gland.
 11. A steerable catheter, comprising: acatheter shaft; a control handle coupled to the catheter shaft, thecontrol handle comprising: a housing assembly having a proximal portionand a distal portion and defining a central axis, wherein the proximalportion defines a central bore concentric with the central axis, thecentral bore including a radial step that defines a shoulder concentricabout the central axis; a resistance adjusting assembly coupled to adistal end of the housing assembly, wherein the resistance adjustingassembly defines a bearing surface disposed at a distal end of theresistance adjusting assembly, the radial step and the bearing surfacedefining a gland; a deformable gasket disposed adjacent to the radialstep; and a tapered glide assembly disposed within the central bore ofthe housing assembly, the tapered glide assembly comprising a frustumwhich extends into and beyond the central bore of the housing assembly,the frustum defined by an angled glide surface extending along theentire longitudinal length of the frustum, wherein the angled glidesurface is tapered radially inward from a proximal edge to a distal edgeof the angled glide surface, and wherein the angled glide surface is incontact with the deformable gasket in the central bore of the housingassembly, wherein translation of the tapered glide assembly in thedistal direction causes a distal end of the catheter to deflect.
 12. Thesteerable catheter of claim 11, further comprising structure thatdefines a port on a proximal end of the proximal portion of the housingassembly, the port being concentric with the central axis and extendingproximal to the shoulder of the central bore, the resistance adjustingassembly being disposed in the port.
 13. The steerable catheter of claim12, wherein the port includes a threaded portion that engages theresistance adjusting assembly.
 14. The steerable catheter of claim 13,wherein the bearing surface of the resistance adjusting assembly isdefined by a bushing, the bushing being operatively coupled with thethreaded portion.
 15. A steerable catheter, comprising: a cathetershaft; a control handle coupled to the catheter shaft, the controlhandle comprising: a housing assembly having a proximal portion and adistal portion and defining a central axis, wherein the proximal portiondefines a central bore concentric with the central axis, the centralbore including a radial step that defines a shoulder concentric aboutthe central axis; a deformable gasket disposed adjacent to the radialstep; and a tapered glide assembly disposed within the central bore ofthe housing assembly, the tapered glide assembly comprising a frustumwhich extends into and beyond the central bore of the housing assembly,the frustum defined by an angled glide surface extending along theentire longitudinal length of the frustum, wherein the angled glidesurface is tapered radially inward from a proximal edge to a distal edgeof the angled glide surface, and wherein the angled glide surface is incontact with the deformable gasket in the central bore of the housingassembly, wherein translation of the tapered glide assembly in thedistal direction generates an increased frictional force between thedeformable gasket and the angled glide surface to cause a distal end ofthe catheter to deflect; and wherein translation of the tapered glideassembly in a proximal direction generates a decreased frictional forcebetween the deformable gasket and the angled glide surface to transitionthe distal end of the catheter from deflection to non-deflection. 16.The steerable catheter of claim 15, wherein translation of the taperedglide assembly in the distal direction increases a contact between theangled glide surface and the deformable gasket.
 17. The steerablecatheter of claim 15, wherein translation of the tapered glide assemblyin the proximal direction decreases a contact between the angled glidesurface and the deformable gasket.
 18. The steerable catheter of claim15, wherein the angled glide surface comprises a non-linear glidesurface.